In the field of health and medicine, body temperature or body surface temperature is a piece of important information for human signs.
In the past, people designed and used various kinds of thermometers. However, in order that the influence of ambient temperature can be avoided so as to measure the temperature more accurately, it usually takes a very long time to conduct measurements. As temperature measuring methods, there are contact type and non-contact type. For a contact type, the body temperature is measured by allowing a temperature sensor unit of a thermometer and the body surface temperature to reach an equilibrium state. In such a case, in order not to receive the image of surroundings, the measurement will be generally made in a mouth, or under an armpit. For non-contact type, infrared rays radiated from the body surface are detected and converted into the body temperature. In such a case, in order to avoid the influence of the surrounding infrared rays, the measurement will usually be made in an ear.
Along with the continued research, for the sake of clearly understanding the state of a body, people begin to consider measuring the body surface temperature at the wrist or the like, and put forward a wrist type thermometer. When the wrist type thermometer is compared with common thermometers used in a mouth, under an armpit and in an ear, there are many situations of incomplete contact with the body surface in its actual use. Furthermore, because it is worn at the wrist and is easily affected by the surroundings, the measuring precision is not high.